In the night between 18 and 19 July  the Virgin asked Catherine Labouré to mint the medal now popular througout the world
A tiny size — 2 x 1 centimetres — for a message that is infinite, because it is the message of salvation. This should not come as a surprise since contemplating the great in the small is a feature of the Christian dynamic. Nevertheless the Miraculous Medial always gives rise to wonder. It soon moved the masses who gave it the title of "miraculous" for the graces poured out as a fruit of Marian devotion.
It was during the night of 18 to 19 July 1830 that the Blessed Virgin appeared to Catherine Labouré in the chapel in Rue du Bac, Paris, and told her in advance of the mission that was to be entrusted to her: to have a medal minted after the design that the Virgin would reveal to her. The Marian Apparition was also a question of motherly foresight, of advice and of anchorage in the faith, as if to highlight Mary's modernness, given that she warned Catherine of the upheavals that would sweep through France whose streets and squares were to be stained with blood. In fact, days later, the Revolution broke out — the Trois Glorieuses — not without a strong dose of anticlerical violence. This was followed, after a few decades, by events in the Municipality of Paris.
The medal was minted in faithful compliance with the instructions the Virgin had dictated to the novice of the Daughters of Charity in her Second Apparition on 27 November. The overall iconography of the medal, an example of highly effective communication, is totally foreign to any cryptographic, occult or enigmatic claims. Mary reveals, she does not conceal. "With supreme wisdom she inscribed on her medal the most appropriate signs for expressing many things in a very tiny space", Gino Ragozzino noted in La Medaglia Miracolosa. Una lettura esegetica (Padua, Edizioni Messaggero, 2012, € 6 ), a slim tome of 70 pages — another case of the great in the small — which reviews and interprets each one of the 12 inspired signs.
It is an authentic roadmap, duly documented to enable readers — with great or scant theological training — to penetrate the mystery of the Redemption serenely and with the expectation of those setting out on an important journey. It is a journey, precisely, of the mind and of faith; that is to say, from cognition to contemplation.
The erect figure of Mary Immaculate dominates the obverse of the medal. Rays of light emanate from her hands; she stands on the globe, crushing a serpent beneath her foot; the inscription reads: "O Marie, conçue sans peché, priez pour nous qui avons recourse à vous" ["O Mary, conceived without sin, pray for us who have recourse to thee"].
The reverse side of the Miraculous Medal portrays two hearts, one bears the crown of thorns, the other is pierced by a sword with the monogram of an interwoven "M" and "I". They are surmounted by a cross and there is a border of 12 stars.
Among the realities expressed by these symbols may be mentioned the price of redemption, the Virgin's compassion, Mary as the dispenser of every grace, triumphant over evil, Mother and Queen, and the mystery of the Immaculate Conception, to which, in fact, the exclamatory prayer is linked. It is a pressing invitation to pray — prayer for the Virgin at that time of the heated theological discussion of this Marian Mystery, anticipated the Definition of the Dogma on 8 December 1854: Beatissimam Virginem Mariam in primo instanti suae Conceptionis fuisse... praeservatam immunem.
To sum up concisely: one side of the medal shows the shining figure of Mary Immaculate who exercises
her power as an intercessor, radiating graces upon the earthly globe. The other side of the medal shows the intimate union between the Mother and her Son, her sharing with Jesus in the work of reparation of the redemption. Ragozzino says: "the two embossed hearts burn with the same fire of love; two people, the Mother and the Son, and a single cross".
Jean Guitton — who is cited in the book — referred to the effective and unitive message of the medal. He said, "the first side is an image of joy, every source aiming to be poured out, all love to inspire love. But if the medal is turned over, one can see the symbol of the cross and the two hearts that suffer together: thus we enter into the intimacy of the First Mystery".
The first person to certify the supernatural origin of the medal was Sr Catherine's confessor, Jean-Marie Aladel, who gave the order for it to be minted. In less than three years millions of the faithful had already received it and experienced its graces.
Its supernatural origin was recognized by the Church in 1894. That same year Leo XIII authorized the
Feast of Our Lady of the Miraculous Medal and approved the relative office of the Mass.
Our Lady wrote on the medal a treatise of Mariology in miniature. "Of course", Gino Ragozzino pointed out, "she does not ask that this treatise be read and understood in its entirety by everyone. All she wants is for the medal to be worn "confidently", namely, with full trust in her, the Immaculate Mediatrix of grace. Nonetheless she expects her message to be understood and welcomed by those who have the ability and intellect to do so". This is the explicit reason for this book's publication.